Company founder Dave Rochlen was a surfer, originally in Santa Monica, California, then in Hawaii. After reading a Life Magazine article showing Russians looking comfortable attending the beach in bathrobes, Rochlen bought some brightly colored floral fabric and asked his wife Keanuenue to make a short, baggy pair of pajamas with a sewn-up fly and cut-off at the knee. They produced the first pair of Jams on December 25, 1964.

Rochlen quit his job as a systems analyst and started his new company Surf Line Hawaii, Ltd. to make and sell his new product. Soon after his first commercial pairs of Jams were worn at Mākaha, Hawaii, Life magazine ran a two-page spread on Rochlen and a group of his surfing friends in the June 1965 issue. After the article, the Jams line was sold in Bloomingdales, Macy's, and Lord & Taylor.

The Jams look was baggy and bohemian, with wild prints and clashing pinks and greens. It was a clear departure from the more subtle color combinations and detailing of existing boardshorts.

Rochlen explained the name as "I thought of it. It's part of the word 'pajamas,' of course, and it was what I wanted – short, quick, jargon, hip, young, one-syllable."